Exoskeletal leg prosthesis and method for alignment

ABSTRACT

An ankle block for a leg prosthesis comprising an insert having a body with an upper mounting surface and a bottom interface surface opposite from the upper mounting surface. The insert body defines a central coaxial hole therethrough. An over mold is formed about an exterior of the body and extends upwardly therefrom defining a central cavity above the insert and above the upper mounting surface.

This application claims the benefit of U.S. Provisional Application No.60/237,859, filed Oct. 4, 2000.

BACKGROUND

The present invention relates to lower leg prostheses and methods ofassembly and alignment of lower leg prostheses and more particularly toan improved apparatus and method of assembly and alignment.

Traditionally there are two types of lower leg prostheses, an externalor exoskeletal apparatus and an internal or endoskeletal apparatus. Theexoskeletal apparatus consists of a rigid leg component shaped in theappearance of the external human leg, attached to a foot. Traditionally,the leg component was constructed of solid wood, but now it is morecommonly constructed of a resin or lightweight composite material formedaround a solid structural foam interior. The composite laminate legcomponent is extremely lightweight, strong, and capable of supportingvery heavy loads. The leg component is attached to the limb of a personthrough a socket. The leg component is attached to an artificial footthrough a block in the ankle area. The ankle block is usually solid woodor structural foam and contains a fastening mechanism such as a bolt andnut fastener to attach the artificial foot and the ankle block isusually permanently attached to the leg portion through the laminate ofthe leg component.

The method of forming the exoskeletal leg apparatus and aligning thesocket and foot for a particular patient traditionally involves aninitial bench alignment based on the experience of the prosthetistconstructing the apparatus. The alignment of the apparatus is extremelyimportant to the effectiveness and comfort of the finished device. Afterthe leg portion is cast and attached to the ankle block furtheralignment of this portion is impossible without cutting the cast portionand re-constructing it. The only adjustment easily made by theprosthetist after forming the exoskeletal leg is the minor adjustment offoot rotation made possible through the foot fastener. Thus, dueprimarily to the alignment difficulty, the modern trend has been awayfrom the exoskeletal leg prosthesis toward a more adjustableendoskeletal leg.

The endoskeletal leg apparatus comprises a series of tubes, simulatingthe bones of the leg, connected via adjustable components to theartificial foot and covered by a cosmetic cover to look like a humanleg. The endoskeletal components are traditionally lightweight metalsinterconnected with fasteners and adjustable components. The advantageof the endoskeletal leg is that all of the components remain adjustableand are easily maintained and replaced if necessary. The components havealso been standardized by many manufacturers for easy interchangeabilityand modularity. The main advantage of the endoskeletal apparatus is theability for the prosthetist to align the leg by adjusting the componentsafter the leg is statically and dynamically loaded by the end userduring a fit test process. The process includes attaching a completelyassembled apparatus including a foot to a user and allowing the user tostand and walk on the leg to determine the proper alignment. During thisprocess, minute adjustments are made perfecting the alignment of the legresulting in a more comfortable and effective prosthesis. Thedisadvantage of the endoskeletal leg is its relative high cost, itsweight, its complexity, its noise potential due to multipleinterconnected metal components, its mechanical appearance, and itslower strength capabilities as compared to the exoskeletal apparatus.

Thus what is desired is an improved apparatus and method of constructingand aligning an exoskeletal leg prosthesis.

SUMMARY OF THE INVENTION

One aspect of the present invention is an ankle block for a legprosthesis. The ankle block comprises an insert having a body with anupper mounting surface and a bottom interface surface opposite from theupper mounting surface. The insert body defines a central coaxial holetherethrough. An over mold is formed about an exterior of the body andextends upwardly therefrom defining a central cavity above the insertand above the upper mounting surface.

Another aspect of the present invention is a method of constructing anexoskeletal leg prosthesis. The method comprises the steps of forming aleg socket for receiving the leg of a user and affixing a temporaryadapter to a bottom of the leg socket. An ankle block is attached to thetop of a prosthetic wherein the ankle block includes an insert forattaching the block to the foot and an outer mold molded over the insertand having an upwardly extending portion defining a recess therein. Atemporary adapter is affixed to an upper surface of the ankle block andan endoskeletal pylon system is attached to the adapters on the ankleblock and the leg socket to create a temporary adjustable prostheticleg. The endoskeletal pylon is adjusted to align the prosthetic footwith respect to the leg socket. After the prosthetic foot is alignedwith the leg socket, the prosthetic foot is removed from the ankleblock. The adjusted leg is retained in a fixture whereupon theendoskeletal pylon and temporary adapters are removed while maintainingthe leg socket and ankle block in their adjusted alignment. A structuralfoam support is molded between the leg socket and the ankle block andthen an outer structural shell is laminated to the combined leg socket,foam support, and ankle block. The prosthetic foot is then reattached tothe ankle block.

Yet another aspect of the present invention is a method for constructingan exoskeletal prosthetic leg. The method comprises the steps ofproviding a leg socket and an ankle block affixed to a prosthetic foot.A temporary adjustable endoskeletal pylon is attached between the legsocket and the ankle block. The pylon is adjusted to dynamically alignthe prosthetic foot with respect to the leg socket. The pylon isadjusted in a dynamic fashion to align the prosthetic foot with respectto the leg socket. The aligned prosthetic leg is then clamped in afixture and the temporary endoskeletal pylon is removed whilemaintaining the adjusted alignment of the leg socket with respect to theankle block. An inner foam core is constructed between the leg socketand the ankle block and a laminated shell is then applied to an exteriorof the combined leg socket, foam core, and ankle block.

These and other advantages of the invention will be further understoodand appreciated by those skilled in the art by reference to thefollowing written specification, claims and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exoskeletal leg prosthesis embodyingthe present invention.

FIG. 2 is a perspective view of a prosthetic foot with an ankle blockattached thereto and the temporary endoskeletal pylon.

FIG. 3 is a cross-section of the prosthetic foot and temporaryendoskeletal pylon of FIG. 2.

FIG. 4 is an exploded view of the attachment of the prosthetic footankle to the temporary endoskeletal pylon.

FIG. 5 is a perspective view of an ankle block.

FIG. 6 is a cross-section of the ankle block of FIG. 5 and the pyramidadapter tool.

FIG. 7 is bottom perspective view of the attachment of the ankle to theankle block.

FIG. 8 is a cross-section of a spacer.

FIGS. 9A-J is a stepped sequence of the construction of an exoskeletalleg embodying the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

For purposes of description herein, the terms “upper”, “lower”, “left”,“rear”, “right”, “front”, “vertical”, “horizontal”, and derivativesthereof shall relate to the invention as oriented in FIGS. 2-3. However,it is to be understood that the invention may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings, and described in thefollowing specification, are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions and other physical characteristics relating to theembodiments disclosed herein are not to be considered as limiting,unless the claims expressly state otherwise.

Turning to the drawings, FIG. 1 shows an exoskeletal prosthetic leg 20which is one of the preferred embodiments of the present invention andillustrates its various components. Exoskeletal leg prosthesis 20includes a leg portion 22 having at an upper portion thereof a legsocket 26 defining a cavity 28 for receiving the leg of a user. Thesocket 26 is supported by leg support 30. Leg support 30 is constructedof a structural foam core 34 and further wherein socket 26 andstructural foam core 34 are encased in a shell 32. Shell 32 is typicallyconstructed of a fiber-reinforced resin, or more commonly known as acomposite shell, the lay up and construction of which is well known inthe art. A foot portion 24 is attached to the bottom of leg portion 22.

Turning now to FIGS. 2-4, a temporary leg assembly 40 is shown whereinfoot portion 24 covered by foot shell 38 has an ankle block 80 attachedthereto. A temporary endoskeletal pylon 44 is affixed to ankle block 80.Temporary endoskeletal pylon 44 comprises an endoskeletal tube 50 havinga tube adapter 52 affixed at a bottom thereof and a socket adapter 46affixed at a top thereof. Socket adapter 46 is temporarily affixed tosocket 26 in a manner that is well known in the art whereby socket 26has a pyramid portion 27 (FIG. 9B) affixed to a bottom thereof which isreceived in socket adapter 46 and retained in place by set screws 48bearing upon individual faces of the pyramid. In this manner, temporaryendoskeletal pylon 44 can be retained and adjusted with respect tosocket 26 by adjusting set screws 48.

FIG. 3 discloses a prosthetic foot 36 and attached ankle 56. Theconstruction of foot 36 and ankle 56 is similar to the construction ofthe prosthetic foot assembly disclosed in U.S. Pat. No. 6,129,766, whichis hereby incorporated by reference. Further description of the foot 36and interface with ankle 56 is not discussed herein. Foot 36 and ankle56 are received in cosmetic foot shell 38 to provide the aestheticappearance of a human foot. Foot shell 38 has an upper surface 39, whichgenerally defines an opening through which the foot 36 and ankle 56 arereceived. Ankle 56 differs from the ankle in U.S. Pat. No. 6,129,766 inthat ankle 56 includes a spherical top attachment surface and a taperedattachment hole 58 centrally located therein. Tapered bolt insert 59 isreceived in attachment hole 58 such that the narrow portion of thetapered insert 59 is oriented toward the top. A foot bolt 60 is insertedthrough tapered insert 59 and ankle 56 from the bottom such that thethreads of bolt 60 extend upwardly through ankle 56 and insert 59.

An ankle block 80 as shown in FIGS. 5-6 is attached to ankle 56 withfoot bolt 60. Referring now to FIGS. 5-6, ankle block 80 comprises aninsert 84 which is typically a machined aluminum structure since a majorobjective of prosthetic construction is to minimize the weight thereof.Insert 84 includes a machined mounting surface 85, which includes fourthreaded holes 86 circumferentially spaced therearound. Insert 84further defines a central hole into which is received a threaded insert88. Threaded insert 88 can be made from steel or titanium or othersturdy metal for receiving the threaded end of foot bolt 60. The bottominterface surface 90 of insert 84 is spherically concave, the radius ofwhich mates with the spherical radius of the upper surface 57 of ankle56. A circular recess 92 is formed in the top of spherical interfacesurface 90 and an alignment pin 91 is interferingly received in a holein insert 84 such that one end of pin 91 extends into the recess definedby spherical interface surface 90. The portion of pin 91 that extendsinto spherical recess 90 is received in a like placed recess ofspherical mounting surface 57 on ankle 56 to ensure a desired rotationalalignment between ankle block 80 and ankle 56. A cap 89 is affixed overa top end of threaded insert 88 to seal the space above insert 84 fromthe threaded hole in insert 88. A urethane overmold 82 is molded aroundbody 81 of insert 84. Urethane overmold 82 is rigid and extends upwardlyfrom insert 84 to form a cup like structure thereby defining a centralrecess. Notches 83 are formed in over mold 82 for access as to thecentral recess for the purpose described below. As seen in FIG. 3, theexterior contour of over mold 82 is slightly smaller than the outerperimeter of upper surface 39 of foot shell 38. As the final prosthesisis an exoskeletal prosthesis, the slightly smaller periphery of urethaneover mold 82 from that of upper surface 39 accommodates the thickness ofthe composite shell 32 to be formed later, thus providing a smoothtransition from foot shell 38 to the exterior surface of composite shell32.

Referring to FIGS. 4 and 6, a pyramid adapter tool 94 is placed onmounting surface 85 of ankle block 80 and is fastened thereto with fourcap screws threaded into threaded holes 86 of insert 84. Pyramid adaptertool 94 has at a top thereof a pyramid 96 with a plurality of pyramidfaces 97 therearound, which in the present embodiment comprises fourpyramid faces. Pyramid adapter tool 94 has a spherical upper surface 98from which pyramid 96 extends at a top center of tool 94.

As seen in FIGS. 3 and 4, endoskeletal leg 44 is affixed to pyramidadapter tool 94 wherein tube adapter 52 is received over pyramid 96 andset screws 54 are threaded to bear against pyramid faces 97. Onesetscrew 54 is aligned with each face of pyramid 96. This method ofattaching leg 44 to pyramid 96 is the same as the attachment of socketadapter 46 to the pyramid affixed to leg socket 26.

In use, and as illustrated in FIGS. 9A-J, the prosthetist will, throughhis experience and expertise, work with the wearer of prosthetic leg 20in a dynamic manner to adjust foot portion 24 with respect to socket 26to provide the optimum alignment of foot portion 24 with respect tosocket 26. The alignment is accomplished by repeated adjustments of setscrews 48 to adjust endoskeletal pylon 44 with respect to socket 26 andby adjusting set screws 54 in tube adapter 52 to adjust foot portion 24,including ankle block 80, with respect to endoskeletal pylon 44 andsocket 26. Notches 83 formed in the upper portion of urethane molding 82facilitate the necessary access to set screws 54.

Once the foot portion 24 has been optimally aligned with leg socket 26(FIGS. 9C-D), the prosthesis is removed from the user's leg and insertedinto a fixture (FIG. 9E). Fixtures for holding leg prostheses foradjustment and work thereon are well known in the art, and thus specificdetails are not illustrated herein. The prosthesis is clamped into thefixture 18 such that both foot portion 24 and leg socket 26 areindividually affixed to the fixture. Once the leg socket 26 and foot 24are retained in their adjusted relationship, endoskeletal pylon 44 isremoved from between leg socket 26 and ankle block 80 (FIG. 9F). Onceendoskeletal pylon 44 has been removed, cap screws 95 are removed frompyramid adapter tool 94 and pyramid adapter tool 94 is removed fromankle block 80. Once the pylon 44 and tool 94 have been removed, aflexible plastic sleeve 100 such as a plastic bag is affixed to a lowerportion of leg socket 26 and to the exterior surface of urethane overmold 82 of ankle block 80. An expanding structural foam 102 is thenplaced in the bag and allowed to expand and cure. Once the foam hascured, the plastic bag can be removed and the foam core extending fromthe leg socket 26 to ankle block 80 can be trimmed and shaped to adesired configuration and in a manner known in the art (FIG. 9I). Afterthe structural foam core has been shaped, either in the shape of a humanleg or some other desired shape, the fiber reinforced shell 32 isconstructed to extend from the upper surface 39 of foot shell 38 to thetop opening of cavity 28 in leg socket 26. The construction of the fiberreinforced shell 32 can be accomplished in any of a number of knownmethods depending upon the type of fiber reinforcement and curableresins utilized to fabricate the shell 32. Once the shell has cured, theleg prosthesis 20 is ready for use by the wearer whereby foot portion 24is reattached (FIG. 9J) and is optimally aligned with leg socket 26 witha lightweight composite type construction therebetween and not relyingon multiple mechanical interfaces that have the potential to becomemisaligned, loose, or create undesirable noise.

When a leg prosthesis such as prosthesis 20 is fabricated for a child,it is also desirable to accommodate for the child's growth withoutrequiring the complete construction of a new prosthesis for every growthincrement of the child. To facilitate the growth adjustment for a child,a spacer 62 as shown in FIG. 8 is provided. Spacer 62 comprises a body69 which has a spherical upper surface 64 and a like spherical bottomsurface 65 wherein spherical surfaces 64 and 65 have the same radius asspherical mounting surface 57 on ankle 56 and concave sphericalinterface surface 90 in ankle block 80. Spacer 62 includes a raisedcircular boss 67 in axial alignment with a vertical hole 70 through acenter of spacer 62. Bottom surface 65 also includes an axially centeredcircular recess 68 slightly larger in diameter than raised boss 67.Upper surface 64 also defines a recess 66 proximate to an outerperiphery of spacer 62. An alignment pin 63 extends from bottom surface65 and is positioned 180 degrees opposite from recess 66.

As illustrated in FIG. 7, when the prosthesis needs to be compensatedfor a child's growth, foot 36 is removed from ankle 56 and foot bolt 60is removed, thus disassembling ankle 56 from ankle block 80. Spacer 62is placed in concave recess 90 of ankle block 80 such that alignment pin91 is received in alignment recess 66 of spacer 62 and ankle 56 is thenmated to the bottom of spacer 62. Boss 67 of spacer 62 is received incircular recess 92 of ankle block 80 to assure axial alignment of spacer62 with ankle block 80 and alignment pin 63 is received in acorresponding alignment recess in ankle 56. A longer foot bolt 60 isthen inserted from the bottom of ankle 56 and threaded into ankle block80 whereupon foot 36 is again reattached to ankle 56. Spacer 62 istypically 0.250 inches in thickness, and up to two spacers can beutilized between ankle block 80 and ankle 56, thus providing for ½ inchof growth accommodation for a child wearing the prosthesis.

In the foregoing description those skilled in the art will readilyappreciate that modifications may be made to the invention withoutdeparting from the concepts disclosed herein. Such modifications are tobe considered as included in the following claims, unless these claimsexpressly state otherwise.

What is claimed is:
 1. A leg prosthesis comprising: a leg portion havingan upper end defining a leg socket for receiving the leg of a usertherein and a lower end; an ankle block supported at said lower end forattachment to a foot portion and including; a metal insert having anupper mounting surface and an oppositely facing interface surface thatis spherical and concave and defining a central hole extending betweensaid surfaces, and an overmold of plastic material surrounding andimbedding the exterior of said insert and extending upwardly from abottom of the insert in a cup shape to define a peripheral wallsurrounding a hollow central cavity exposing said upper mounting surfaceat the bottom of said cup shape.
 2. A leg prosthesis as set forth inclaim 1 wherein said peripheral wall defining said cup shape includesnotches extending downwardly thereinto.
 3. A leg prosthesis as set forthin claim 2 wherein said lower end of said leg portion includes astructural plastic material molded about said cup shape and into saidcavity thereof.
 4. A leg prosthesis as set forth in claim 3 including acap disposed on said upper surface to cover said central hole to preventsaid structural plastic from entering said hole.
 5. An ankle block for aleg prosthesis comprising; a metal insert having an upper mountingsurface and an oppositely facing bottom interface surface and defining acentral hole extending between said surfaces for attachment to aprosthetic foot, said bottom interface surface being concave about saidcentral hole, an over mold of plastic material surrounding and imbeddingthe exterior of said insert and extending upwardly in a cup shape todefine a central cavity exposing said upper surface at the bottom ofsaid cup shape.
 6. An ankle block as set forth in claim 5 wherein saidcup shape includes notches extending downwardly thereinto.
 7. An ankleblock as set forth in claim 5 including an internally threaded insertdisposed in said central hole.
 8. An ankle block as set forth in claim 7wherein said internally threaded insert includes an enlarged headoverlying said central hole adjacent said upper surface for retainingsaid internally threaded insert in said hole.
 9. An ankle block as setforth in claim 8 including a cap covering said threaded insert.
 10. Anankle block as set forth in claim 5 wherein said bottom surface of saidinsert has a circular recess surrounding said central hole.